Сибирский федеральный университет

Тип публикации: статья из журнала

Год издания: 2021

Идентификатор DOI: 10.1016/j.gr.2020.09.007

Ключевые слова: altai-sayan rift system, devonian magmatism, incompatible elements, plume-lithosphere interactions, sr-nd isotopes

Аннотация: The geodynamic environment of the 407–392 Ma Altai-Sayan Rift System is characterized using previously published and new original data on whole rock, trace and Sr-Nd isotopic compositions, along with U-Pb zircon ages. Five magmatic associations are present: basalt (basalts and basaltic trachyandesites), continuous (basalts, andesites, dacite-rhyolites), alkaline (basalts, nephelinite, tephrite, phonotephrite, phonolite, teralite, ijolite-urthite, foyaite, nepheline and alkaline syenite), bimodal (trachybasalts, trachyrhyolites-pantellerites and peralkaline granites) and ultramafic-mafic (picrites and picrodolerites). Mafic rocks of basalt, continuous, alkaline, and bimodal associations exhibit a wide variation of TiO2 (from 1.05 to 4.05 wt%) and are compositionally intermediate between intraplate basalts of OIB type and basalts of active continental margins IAB type. The TiO2 content in these mafic rocks correlates directly with the content of large ion lithophile elements (LILE), rare-earth elements (REE), high field strength elements (HSFE), and particularly with Nb and Ta. The basaltic samples have positive εNd(395) values (+3.4 to +7.7) and a large range of εSr(395) values (−13.6 to +12.6). εSr(395) decreases with increasing TiO2 abundance. Pantellerites and alkaline granites have ore-level concentrations of Nb, Ta, Zr, Hf, REE; and they have similar Sr and Nd isotope parameters to those of the high-Ti basalts. This indicates their origin via fractionation of mantle magmas. Rhyolite samples are depleted in rare incompatible elements, but have low positive εNd(395) values (+1.5 to +1.8), and εSr(395) values (+16.6 to +20.6), and they compositionally resemble the rocks produced from anatectic magmas of crustal origin. Whole-rock elemental and isotopic data suggest that the mafic rocks were likely derived from lithospheric mantle that was metasomatized during the prior Caledonian accretion/subduction event. In combination with the field relationship and regional geology, our study suggests that the rock associations from the Devonian Altai-Sayan Rift System were derived by the activity of mantle plumes. © 2020 International Association for Gondwana Research

Журнал: Gondwana Research

Выпуск журнала: Vol. 89

Номера страниц: 193-219

ISSN журнала: 1342937X

Издатель: Elsevier Inc.

• Vorontsov A. (Institute of Geochemistry, Russian Academy of Sciences, Siberian Branch, Irkutsk, Russian Federation, Irkutsk State University, Irkutsk, Russian Federation)
• Yarmolyuk V. (Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Moscow, Russian Federation)
• Dril S. (Institute of Geochemistry, Russian Academy of Sciences, Siberian Branch, Irkutsk, Russian Federation)
• Ernst R. (National Research Tomsk State University, Tomsk, Russian Federation, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada)
• Perfilova O. (Siberian Federal University, Krasnoyarsk, Russian Federation)
• Grinev O. (National Research Tomsk State University, Tomsk, Russian Federation)
• Komaritsyna T. (Institute of Geochemistry, Russian Academy of Sciences, Siberian Branch, Irkutsk, Russian Federation)

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